‰ NOW 35 WPM ‰ TEXT IS FROM OCTOBER 2012 QST PAGE 44‰
THE SHARED APEX LOOP ARRAY THIS COMPACT DIRECTIONAL WIDEBAND RECEIVING
ANTENNA CAN REDUCE INTERFERENCE. MARK BAUMAN, KB7GF EFFECTIVE RECEIVING
ANTENNAS ARE BECOMING AN INDISPENSIBLE PART OF OUR AMATEUR ARSENAL AS WE
BATTLE INTERFERENCE FROM BOTH NATURAL AND MAN MADE SOURCES. MANY OF US DO
NOT HAVE THE ACREAGE TO ERECT DIRECTIONAL ANTENNAS, ESPECIALLY ON THE LOWER
BANDS, SO WE USE SHORTENED VERTICALS AND LOW HANGING DIPOLES, WHICH PROVIDE
ESSENTIALLY OMNIDIRECTIONAL RESPONSE. AS A RESULT, OUR EARS ARE BOMBARDED
WITH SIGNALS AND INTERFERENCE FROM ALL DIRECTIONS WHEN OUR TRANSMITTING
ANTENNA DOUBLES AS OUR RECEIVING ANTENNA. ANTENNA CONCEPT TO ASSIST IN
THIS BATTLE, I DESIGNED A COMPACT DIRECTIONAL RECEIVING ANTENNA THAT
EFFECTIVELY REDUCES INTERFERENCE OVER A WIDE FREQUENCY RANGE. THE ARRAY
DESCRIBED HERE IS COMPACT, HAVING A LOOP SPACING OF ONLY 2 INCHES, A 10
FOOT TALL MAST, AN ARRAY LENGTH OF 20 FEET AND A BASE HEIGHT OF 6 INCHES.
IN THIS CONFIGURATION, THE ARRAY DELIVERS DIRECTIVITY OVER A FREQUENCY
RANGE OF 500 KHZ TO 22 MHZ AND EXCEPTIONAL SENSITIVITY ABOVE 6 MHZ. A
GROUND MOUNTED VERSION OF THE SHARED APEX LOOP ARRAY IS SHOWN IN FIGURE 1
AND SCHEMATICALLY IN FIGURE 2. THE ANTENNA UTILIZES TWO CLOSELY SPACED
LOOPS THAT ARE INTERCONNECTED VIA A DELAY LINE TO DELIVER HEALTHY FRONT TO
SIDE AND FRONT TO BACK RATIOS OVER A WIDE FREQUENCY RANGE. A NON
‰ END OF 35 WPM TEXT ‰ QST DE W1AW ƒ